1. Field of the Invention:
The present invention relates to a process for the decomposition of dihydroperoxide to resorcinol, and more particularly to the catalytic decomposition of m-diisopropylbenzene dihydroxide.
2. Description of the Prior Art:
In 1972, researchers at the Stanford Research Institute (SRI) reviewed a new route for the preparation of resorcinol via hydroperoxidation. The SRI process involves production of m-diisopropylbenzene (m-DIPB) by alkylation of benzene and/or cumene with propylene, followed by the oxidation of m-DIPB to diisopropylbenzene dihydroperoxide (m-DHP) and other by-products. The DHP is then decomposed to resorcinol and acetone with the aid of an acid catalyst.
Numerous methods have since been proposed to improve upon the preparation of resorcinol by the hydroperoxidation route.
The decomposition of m-DHP to resorcinol is usually carried out in the liquid phase, in a substantially anhydrous organic solvent, such as acetone, methyl isobutyl ketone (MIBK), benzene, or toluene. The decomposition is highly exothermic, and produces one mole of resorcinol and two moles of acetone from each mole of m-DHP. Small quantities of strong acids, for example sulfuric acid or orthophosphoric acid (H.sub.2 SO.sub.4 and H.sub.3 PO.sub.4, respectively), are used as catalyst. ##STR1##
The rate of DHP decomposition is thought to be first order based on DHP; it is accelerated by acid and by resorcinol but retarded by water. All hydroperoxides present in the feed will be converted to acetone and corresponding phenolic products. Thus, other oxidation by-products such as m-monohydroperoxides (m-MHP) will form m-isopropylphenol and m-hydroxyhydroperoxides (m-HHP) will form m-(alpha-hydroxyisopropyl)phenol, which immediately dehydrates to m-isopropenylphenol.
According to the SRI review referenced above, the MIBK extract of m-DHP is evaporated to produce a 50% solution of hydroperoxides. Concentrated sulfuric acid (0.2 wt %), as catalyst, and 70% hydrogen peroxide (25% excess) to oxidize HHP and the dicarbinols (DCL), are added to this solution in a continuous reactor at 80.degree. C. The addition rates are such that an eight minute residence time is achieved. After the cleavage, the sulfuric acid is neutralized with a slurry of hydrated lime and the solids are removed by filtration. The filtered cleavage product is distilled to remove acetone and MIBK. The aqueous distillation bottom is extracted with toluene to selectively remove impurities (isopropylphenol and heavy ends) from the aqueous resorcinol solution. The purified aqueous raffinate is evaporated to remove part of the water. The concentrated aqueous solution is allowed to grow crystals. Finally, the resorcinol is separated by centrifugation and dried.
However, according to British Patent Specification No. 1,455,450, published in 1976, only by using pure m-DHP for the acid-catalyzed decomposition can relatively pure resorcinol be obtained. When product from the hydroperoxidation of m-DIPB is directly used in the decomposition, the resulting reaction product contains, besides resorcinol and the compound produced from other hydroperoxides, a number of other secondary products formed by subsequent reactions of the decomposition components and products under the action of acid catalyst. Resorcinol and acetone react to form resins and resorcinol and isopropenylphenol react to give a high-boiling adduct. The isopropenylphenol also polymerizes to give both liquid and solid polymers. The chemistry involved when a DHP/HHP mixture is decomposed in the presence of acid-catalyst is presented below. ##STR2##
Similarly, Suda et al. U.S. Pat. No. 3,923,908 to Sumitomo Chemical Company discussed the relationship between DHP purity and the resorcinol yield from its decomposition. The yields of resorcinol are highly dependent on the amount of impurities containing the 2-hydroxy-2-propyl group, such as carbinols and HHP. Best results (90-95% yields) are obtained when the ratio of these groups to the number of molecules of DHP is below 0.16. In other words, the mol % HHP in the DHP/HHP sample can not be greater than 14%. A way to obtain such a high purity DHP/HHP sample is not mentioned in the patent.
Imai et al. U.S. Pat. No. 4,339,615 to Mitsui Petrochemical Industries discloses a process for producing resorcinol, which comprises cleaving pure m-DHP in the presence of a water-soluble acid catalyst (sulfuric acid in acetone) in a mixed solvent consisting of an aromatic hydrocarbon and acetone. An 86% resorcinol yield is reported using a DHP/HHP sample containing 3.9 mol % HHP. The pure DHP probably is obtained by treating their hydroperoxidation product with hydrogen peroxide.
British Patent Application No. GB 2 071 662 A discloses the use of superacid catalysts, such as boron trifluoride-hydrogen fluoride complex in the preparation of resorcinol from m-DIPB.
Many patents have disclosed procedures for the purification of crude resorcinol obtained by decomposing m-DHP with acid catalysts. For example, a Japanese patent, Japan Kokai No. 78-53626, issued to Sumitomo Chemical Company claims a simple distillation process to obtain pure resorcinol. Crude resorcinol from the DHP decomposition is distilled in vacuo at less than 210.degree. C. pot temperature to effectively remove impurities produced in the acid-catalyzed decomposition.
Another patent, Hashimoto et al. U.S. Pat. No. 4,239,921, issued in 1980 to Mitsui Petrochemical Industries, discloses an improved resorcinol purification by solvent recrystallization. The patent claims that both low-boiling and high-boiling impurities can be removed from the crude resorcinol by a recrystallization process using a mixed solvent consisting of a specific ratio of an aromatic hydrocarbon, an alkylphenol, and an acylphenol. For example, the resorcinol recrystallized from a mixture of toluene-isopropylphenol has only 30 ppm of high boiling and 60 ppm of low boiling impurities.
An object of the present invention is to improve the yields of resorcinol obtained from the decomposition of m-DHP.